text: 
  exports.up = function (knex) {
  	return knex.schema.table('books', books => {
  		books
  			.text('image_url')
  			.nullable();
  
  	});
  }
  
  exports.down = function (knex) {
  	return knex.schema.table('books', books => {
  		books.dropColumn('image_url');
  	});
  };